A copper wire of length 3 m is stretched by 3 mm by applying an external force. The volume of the wire is $$600 \times 10^{-6}$$ m³. The elastic potential energy stored in the wire in stretched condition would be _______  J :
(Given Young's modulus of copper $$ = 1.1 \times 10^{11}$$ N/m²)

$$U = \frac{1}{2} \times \text{Stress} \times \text{Strain} \times \text{Volume}$$

$$U = \frac{1}{2} \times Y \times (\text{Strain})^2 \times \text{Volume}$$

$$\text{Strain} = \frac{\Delta L}{L} = \frac{3 \times 10^{-3}\text{ m}}{3\text{ m}} = 10^{-3}$$

$$U = \frac{1}{2} \times \left(1.1 \times 10^{11}\right) \times \left(10^{-3}\right)^2 \times \left(600 \times 10^{-6}\right)$$

$$U = \frac{1}{2} \times 1.1 \times 10^{11} \times 10^{-6} \times 600 \times 10^{-6}$$

$$U = 330 \times 10^{-1} = 33\text{ J}$$